This invention relates generally to integrated circuit manufacturing methods and more particularly to methods for manufacturing integrated circuits having both bipolar devices and complementary metal-oxide-semiconductor (CMOS) silicon gate field effect devices formed on a single crystal substrate.
As is known in the art many integrated circuits have been made using bipolar transistor devices and many other integrated circuits have been made using CMOS field effect devices. Bipolar devices provide excellent performance in linear integrated circuits, such as in amplifier circuits, whereas CMOS devices provide excellent performance in switching or logic circuits. In many applications it is therefore desirable to use circuits which employ both bipolar devices and CMOS devices, such as digital to analog converters. In such application, however, the bipolar devices are generally formed as one chip or integrated circuit and the CMOS devices are formed as a second chip, the two chips then being electrically interconnected by a printed circuit board. In order to reduce the size of the converter it would be desirable to form both the bipolar devices and the CMOS devices on a single chip; however, because the processing requirement in forming both types of devices are not readily compatible, methods used to provide such single chip on a commercially practical basis have generally not heretofore been successful.